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Fig. 5. The transmission loss as a function of frequency, for various propagation distances. It contains contributions to sound attenuation from geometrical spread- ing losses and atmospheric absorption. The reference distance in the transmission calculation is 1 m from the source. The colors (line types) indicate the different source-receiver distances: blue (solid) = 10 m; red (dash) = 20 m; green (dot-dash) = 50 m; black (dot) = 100 m.
Taken in isolation, the fluid loading on a Venusian guitar string would be much less than the loading on a drum or pipe, since a vibrating wire sets much less gas into motion53 (although of course, fluid loading on other structures, such as the body of the guitar, would also need to be considered).
The fact that Venus has the opposite effect with flue and reed pipes on the same instrument shows that the effect of an alien world on the sound generated by a given musical instru- ment therefore depends on the details of the mechanism by which that sound is generated. Additional degrees of freedom in the problem are available in the choice of materials used for construction and the extent to which adjustments are made to compensate for unwanted effects—while for example a wire can be tuned by altering its tension to counteract the effects of thermal expansion on Venus, the effect of Venus’ temperature on the waves in the walls of a bell cannot be so easily counter- acted. Indeed, the philosophy of wishing to counteract the alien effects is short-sighted, as the new sounds provide the artist with a palette of acoustic “colors” not available on Earth. Such considerations transpose the study of extraterrestrial music from science to art that might include planetarium experiences for the seeing and the visually impaired alike, more realistic soundscapes in science fiction movies, and com- positions that use the sounds of other worlds.
Venus probably presents the most musically interesting of the three alien atmospheres studied, because the fluid loading effect is so great (it is almost negligible on Mars53) and shifts the frequencies in the opposite direction to the
for an adult, and nearly a full octave for a child. This is demonstrated in reference 53. That paper also shows that when considering the effect of fluid loading on other vibrat- ing structures, the geometry and average density of the vibrat- ing solid significantly affect the fluid loading. The density of the material matters, since the proportional significance of any given “added mass” is greater the less massive the original structure. Therefore, all other things being equal, a light car- bon fiber structure (such as a Venusian drumskin) will be more significantly affected than a steel structure of otherwise identical vibrational properties and geometry. Furthermore, the fluid loading effect increases with the momentum of the gas set into motion by the vibrating structure. As a result, the fluid loading on the vocal folds is much greater in the vocal tract than it would be were the vocal folds to vibrate in free space, where geometric spreading would allow the gas vibra- tion amplitude to fall off with distance from the vocal folds.
Sounds in Space 21